The drug 5-aminosalicylic acid rescues alpha 1-proteinase inhibitor from the neutrophil oxidative inactivation. A possible contribution to its therapeutic action in ulcerative colitis.

The glycoprotein alpha 1-proteinase inhibitor is the specific inhibitor of neutrophil elastase, a major tissue-damaging protease. When incubated with activated neutrophils, alpha 1-proteinase inhibitor lost its pancreatic porcine elastase inhibitory capacity and became incapable of forming a sodium dodecyl sulphate-stable complex with pancreatic porcine elastase. Inhibitors and scavengers of neutrophil-derived reactive oxygen species outlined the crucial role of hypochlorous acid in the alpha 1-proteinase inhibitor inactivation. Moreover, the drug 5-aminosalicylic acid prevented the inactivation of alpha 1-proteinase inhibitor by neutrophils in a dose-dependent manner. Finally, when the capacity of 5-aminosalicylic acid to rescue alpha 1-proteinase inhibitor from the neutrophil-derived attack was plotted as a function of the 5-aminosalicylic acid ability to scavenge neutrophil-derived hypochlorous acid, a positive linear relationship was found. Thus, our results provide a direct evidence that 5-aminosalicylic acid is able to prevent the oxidative inactivation of alpha 1-proteinase inhibitor by neutrophils. Therefore, we suggest that the drug has the potential to limit the elastase-mediated damage of colonic connective tissue by creating a microenvironment of active alpha 1-proteinase inhibitor around the neutrophils.     

Sulfasalazine metabolites and dapsone attenuate formyl-methionyl-leucyl-phenylalanine-induced mucosal injury in rat ileum

The effects of 5-aminosalicylic acid (5-ASA), 4-ASA, N-acetyl-5-ASA, and sulfapyridine on mucosal permeability were determined in an experimental model of acute ileitis. In addition, the antiinflammatory drug dapsone was tested. The distal 10 cm of rat ileum was perfused with formyl-methionyl-leucyl-phenylalanine (FMLP) (10(-5) M), a bacterial peptide that activates and attracts neutrophils. Changes in mucosal permeability were assessed using the blood-to-lumen clearance of 51Cr-ethylene-diamineacetate. Luminal FMLP increased 51Cr-labeled ethylenediamineacetate clearance twofold and fourfold in the first and second hour, respectively. Addition of 5-ASA (10 mM), 4-ASA (10 mM), or dapsone (4 mM) to the luminal perfusate after 60 min of FMLP perfusion greatly attenuated the increased mucosal permeability observed after 120 min of FMLP perfusion. Neither N-acetyl-5-ASA (10 mM) nor sulfapyridine (5 mM) had an effect on the FMLP-induced increase in mucosal permeability. We characterized the inhibitory effect of these drugs on the catalytic activity of myeloperoxidase and tested their ability to scavenge hypochlorous acid in vitro. 5-Aminosalicylic acid, 4-ASA, and dapsone demonstrated a powerful inhibitory effect on the catalytic activity of myeloperoxidase, whereas all drugs were equally effective in scavenging HOCl. In additional in vitro experiments we were unable to demonstrate an inhibitory effect of either of the drugs on the catalytic activity of neutrophilic elastase. Our results indicate that inhibition of neutrophilic myeloperoxidase may be an important mechanism by which 5-ASA, 4-ASA, and dapsone attenuate FMLP-induced mucosal injury.     

Candidacidal activity of the neutrophil myeloperoxidase system can be protected from excess hydrogen peroxide by the presence of ammonium ion

Excessive concentrations of hydrogen peroxide inhibit the neutrophil myeloperoxidase system, presumably by inactivating the hypochlorous acid produced by this system. Ammonium ion generated by neutrophils and other cells can react with hypochlorous acid to produce monochloramine, an oxidant with good microbicidal activity, but relative resistance to inactivation by other compounds. In an assay based on the oxidation of 5-thio-2-nitrobenzoic acid, hydrogen peroxide reacted more readily with sodium hypochlorite (used as a source of hypochlorous acid) than with monochloramine. Also, in this assay Candida albicans yeast inactivated the oxidant activity of hypochlorous acid more completely than they did that of monochloramine. The killing of Candida by sodium hypochlorite, as determined in a standard colony count microbicidal assay, was inhibited by equimolar and greater concentrations of hydrogen peroxide; killing of this organism by monochloramine was not affected by a tenfold excess concentration of hydrogen peroxide. In microbicidal assays using 4 mU of myeloperoxidase and optimal or excessive concentrations of hydrogen peroxide or glucose and glucose oxidase to generate hydrogen peroxide, the excessive concentrations inhibited killing of Candida, but not Staphylococcus aureus. The inhibition of Candida killing could be reversed by addition of ammonium ion to convert hypochlorous acid to monochloramine. These results indicate that for certain organisms such as C albicans, conversion of hypochlorous acid to monochloramine by reactions with ammonium ion may extend the range of hydrogen peroxide concentrations under which killing by the myeloperoxidase system can occur by protecting the necessary microbicidal oxidants from inactivation by excess hydrogen peroxide.     

The anti-inflammatory drug nimesulide rescues alpha-1-proteinase inhibitor from oxidative inactivation by phagocytosing neutrophils.

When neutrophils are recruited to tissue sites and exposed to phagocytosable targets, they release oxidants which may be responsible for the local inactivation of alpha-1-proteinase inhibitor (A1PI). Consequently, A1PI becomes incapable of inhibiting the proteolytic activity of elastase, released at the same time by neutrophils as a result of leakage from phagocytic vacuoles. In the present paper we show that phagocytosing neutrophils inactivate A1PI via a process inhibitable by chemical agents known to interfere with the hypochlorous acid (HOCl)-generating myeloperoxidase pathway. The anti-inflammatory drug nimesulide (NMS), which is able to efficiently limit the extracellular availability of HOCl in the neutrophil surroundings, was found to prevent the inactivation of A1PI by neutrophils. The results provide evidence for a possible way to control neutrophil elastase activity by rescuing its natural inhibitor (A1PI) at inflamed tissue sites during infectious and noninfectious processes.     

A dominant negative retinoic acid receptor blocks neutrophil differentiation at the promyelocyte stage.

We have investigated the roles of retinoic acid receptors in the development of neutrophils by using an interleukin 3-dependent multipotent hematopoietic cell line (FDCP mix A4) as well as normal mouse bone marrow cells. Treatment of the FDCP mix A4 cells with murine granulocyte/macrophage-colony-stimulating factor (GM-CSF) induced these cells to differentiate into neutrophils and macrophages. When the endogenous retinoic acid receptor activity in FDCP mix A4 cells was suppressed by a dominant negative retinoic acid receptor construct, this GM-CSF-induced neutrophil differentiation was blocked at the promyelocyte stage. The blocked promyelocytes proliferated continuously as a GM-CSF-dependent cell line but could be induced to terminally differentiate into neutrophils with supraphysiological concentrations of all-trans-retinoic acid (1-10 microM). The ability of the dominant negative retinoic acid receptor to block neutrophil differentiation at the promyelocyte stage was also demonstrated in normal, primary mouse bone marrow cells. Our results indicate that retinoic acid receptors in conjunction with hematopoietic growth factors play a crucial role in the terminal differentiation of normal neutrophil precursors. The system described here may also serve as a model for studying the pathogenesis of human acute promyelocytic leukemia.     

Selective depletion of neutrophils by a monoclonal antibody, RP-3, suppresses dextran sulphate sodium-induced colitis in rats

Administration of dextran sulphate sodium to animals induces acute colitis characterized by infiltration of large numbers of neutrophils into the colonic mucosa, which histologically resembles human active ulcerative colitis. It has been reported that neutrophils and the reactive oxygen metabolites produced by them are involved in the progress of ulcerative colitis. This study was intended to clarify their roles by using this animal model. First, possible sources and species of reactive oxygen metabolites were determined using luminol-dependent chemiluminescence with addition of enzyme inhibitors and reactive oxygen metabolite scavengers. Next, to examine whether neutrophils and hypochlorous acid derived from them contribute to tissue injury, we administered RP-3, a monoclonal antibody capable of selectively depleting neutrophils, and taurine, a hypochlorous acid scavenger, to rats treated with dextran sulphate sodium. Addition of azide, taurine, catalase, superoxide dismutase and dimethyl sulphoxide into colonic mucosal scrapings significantly inhibited chemiluminescence production, but allopurinol and indomethacin had no effects. These results suggest that excessive hypochlorous acid, hydrogen peroxide, superoxide anion and hydroxyl radical are generated by the inflamed colonic mucosa. Intraperitoneal injections of RP-3 significantly suppressed bleeding, tissue myeloperoxidase activity, chemiluminescence production and erosion formation. On the other hand, administration of taurine tended to inhibit bleeding and erosion formation to some extent, although it could not significantly suppress them. These data suggest that neutrophils play an important role in the development of this colitis and that hypochlorous acid might be one of the causes of tissue injury induced by neutrophils.     

Comparison of 5-aminosalicylic acid and N-acetylaminosalicylic acid uptake by the isolated human colonic epithelial cell.

Isolated human colonic epithelial cell suspensions were incubated with either 0.1 mM 5-aminosalicylic acid (5-ASA) or 0.1 mM acetylaminosalicylic acid (Ac-ASA) for up to two hours. Intra- and extracellular 5-ASA and Ac-ASA were measured by high performance liquid chromatography. Mean 5-ASA uptake in one hour was 160.5 nmol/g dry weight, compared with an Ac-ASA uptake of only 5.75 nmol/g dry weight. No unchanged 5-ASA was detected inside the cell. Repeated washing had no effect on the intracellular Ac-ASA concentration. This discrepancy in drug uptake may explain why Ac-ASA seems to be ineffective when given to patients with ulcerative colitis.     

Differences in free fatty acid and glucose metabolism of human blood neutrophils and lymphocytes.

Comparison of isolated human neutrophils and lymphocytes in short-term tissue culture revealed marked differences in their rates of lipid biosynthesis. Ficoll-Hypaque gradients were used to separate lymphocytes and neutrophils from the blood of normal subjects. Neutrophils incorporated more palmitate into cell lipids (151.0 +/- 16.6 nmole/hr/10(8) cells) than lymphocytes (41.6 +/- 4.1). By contrast, the lymphocytes oxidized more palmitate (8.3 +/- 0.5 nmole/hr/10(8) cells) as compared to neutrophils (1.1 +/- 0.1). The greater fatty acid uptake by the neutrophils was due to a sixfold greater rate of incoporation of palmitate into their triglyceride fraction. Triglyceride synthesis by neutrophils increased as the molar ratio of free fatty acid to albumin was raised, whereas incorporation into phospholipids remained relatively constant; there was preferential labeling of neutrophil triglycerides throughout the physiologic range. Studies using linoleate and oleate gave similar results. The distribution of radioactivity into various phospholipids determined by thin-layer chromatography was similar for the two cell types. When labeled glucose was used as a substrate to measure incorporation primarily into the glycerol backbone of the cell lipids, neutrophils incorporated more radioactivity into total lipids and triglycerides than lymphocytes. These results indicate that neutrophils take up much more fatty acid than lymphocytes primarily because they synthesize much larger quantities of triglycerides, a storage form. Since cellular triglycerides may act as a source of fatty acid for lecithin synthesis during phagocytosis, the greater rate of fatty acid incorporation in the neutrophil may reflect a metabolic pattern that permits efficient phagocytosis.     

Products of neutrophil metabolism increase ammonia-induced gastric mucosal damage

Recent studies have indicated that ammonia is involved in the pathophysiology ofHelicobacter pylori-associated gastric mucosal damage.Helicobacter pylori-associated chronic active gastritis is characterized by an invasion of neutrophils. We investigated the interrelationship among hypochlorous acid (oxidant produced by neutrophil), ammonia (product ofHelicobacter pylori urease), and monochloramine (product of ammonia and hypochlorous acid) in the development of gastric mucosal damage in rats. Gastric mucosal lesions were produced by exposure of the gastric mucosa to ammonia, urea with urease, or urea withHelicobacter pylori in rats subjected to ischemia. Pretreatment with taurine (scavenger of hypochlorous acid) or antineutrophil serum significantly attenuated gastric mucosal lesions induced by the above test agents. Ammonia-induced gastric mucosal lesions were exacerbated in the presence of hypochlorous acid with concomitant generation of monochloramine. These results suggest that the ammonia, hypochlorous acid, and monochloramine triad may be important inHelicobacter pylori-mediated gastric mucosal damage.     

Chlorotyrosine protein adducts are reliable biomarkers of neutrophil-induced cytotoxicity in vivo

INTRODUCTION: A limitation for investigating the pathophysiological role of neutrophils in vivo is the lack of a reliable biomarker for neutrophil cytotoxicity in the liver. Therefore, we investigated if immunohistochemical detection of chlorotyrosine protein adducts can be used as a specific footprint for generation of neutrophil-derived hypochlorous acid in vivo. METHODS: C3Heb/FeJ mice were treated with 100 micrograms/kg endotoxin (ET) alone or in combination with 700 mg/kg galactosamine (Gal/ET). Some animals received additionally two doses of 10 mg/kg of the pancaspase inhibitor Z-VAD-fmk. An antibody against chlorotyrosine was used for the immunohistochemical analysis. RESULTS: At 6 h after Gal/ET, hepatocellular apoptosis was evident without increase in plasma ALT activities. Neutrophils accumulated in sinusoids but there was no evidence for chlorotyrosine staining. At 7 h after Gal/ET, about 54% of the sequestered neutrophils had extravasated, there was extensive necrosis and increased plasma ALT activities. Extensive immunostaining for chlorotyrosine, mainly colocalized with neutrophils, could be observed. Treatment with Z-VAD-fmk eliminated apoptosis, necrosis and the increase in plasma ALT values. Neutrophil extravasation was prevented but the overall number of neutrophils in the liver was unchanged. Chlorotyrosine staining was absent in these samples. After ET alone (7 h), sinusoidal neutrophil accumulation was similar to Gal/ET treatment but there was no apoptosis, neutrophil extravasation, ALT release or chlorotyrosine staining. CONCLUSIONS: Chlorotyrosine staining in liver samples correlated well with evidence of neutrophil-induced liver injury in the endotoxemia model. These results indicate that assessment of chlorotyrosine protein adduct formation by immunohistochemistry could be a useful marker of neutrophil-induced liver cell injury in vivo.     

Granulocyte- and granulocyte-macrophage colony-stimulating factors enhance neutrophil cytotoxicity toward HIV-infected cells

Although the control of retroviral disease in animal systems often involves antibody-dependent cell-mediated cytotoxicity (ADCC), the role of cytotoxic function in human retroviral disorders is uncertain. The ability of the neutrophil to kill HIV-infected targets directed by antiviral antibody was examined. Neutrophils from patients with AIDS killed HIV-infected MOLT-3A cells in a manner equivalent to neutrophils obtained from normal volunteers. Both granulocyte- and granulocyte-macrophage colony-stimulating factors (G-CSF and GM-CSF) markedly augmented the cytotoxic function. Studies done with fractionated human antisera revealed that ADCC to HIV-infected cells was mediated only by antibody to the env glycoprotein. ADCC in this system was not dependent on oxidative metabolism because neutrophils from patients with chronic granulomatous disease (CGD) were capable of CSF-augmented cytotoxicity. Although ADCC can be mediated by various classes of lymphocytes and mononuclear phagocytes, such cells may be infected by HIV. Because the neutrophil apparently is not productively infected by the virus, it is an ideal cell to focus on with regard to cytotoxic function in AIDS patients. The findings regarding neutrophil ADCC in AIDS are clinically relevant because the availability of CSFs now permits therapeutic regulation of neutrophils in AIDS patients, and presumably natural antibody may be useful in targeting HIV-infected cells for neutrophil cytotoxicity in vivo.     

Inhibition of neutrophil cytolysin production by target cells

Neutrophils, triggered by heat-aggregated human IgG (Agg.IgG), were found to lyse chicken red blood cells (CRBC) as determined by a 51Cr release method. The lysis was inhibited by azide, catalase, chloride- free medium and amino acids, suggesting the requirement for myeloperoxidase (MPO), hydrogen peroxide (H2O2), chloride ions (Cl-), and hypochlorous acid (HOC1), respectively. These results indicate that neutrophils lyse CRBC through an HOCl-(ie, MPO-H2O2-Cl-) dependent process. Although HOCl can react with neutrophil-derived nitrogenous (N- ) compounds to yield chloramines, the main and well-characterized chloramines did not play a direct role in the lysis of CRBC in our model system. Thus, it appears that lysis is due either to HOCl or to an unknown compound derived from and with characteristics similar to HOCl. When CRBC were replaced with HRBC targets, no lysis could be observed. Treatment of HRBC with carmustine, to inhibit the glutathione cycle, did not affect the cell resistance to lysis by neutrophils. Conversely, the inhibition of HRBC catalase activity with aminotriazole (AT) made the cells susceptible to neutrophil-mediated HOCl-dependent lysis: this suggests that HRBC escape lysis by neutrophils through an AT-inhibitable, ie catalase-dependent, process. Through an identical catalase-dependent process, HRBC were capable of efficiently preventing the H2O2 and HOCl recovery from Agg.IgG-triggered neutrophils, tested under experimental conditions similar to those used for cytolytic assays. Together, these data suggest that HRBC targets, endowed with high catalase activity, escape neutrophil-mediated lysis by consuming (by catalase) neutrophil-derived H2O2, so that HOCl cannot be produced in amounts sufficient to promote lysis. Parallel experiments, performed with AT-treated CRBC, showed that these cells, endowed with a relatively low catalase content, only partially limit neutrophil cytolytic efficiency by a process qualitatively similar to that observed with HRBC targets. The results provide evidence that target cells can restrain neutrophil cytolytic efficiency by interfering with the MPO-H2O2-Cl system through their catalase activity.     

4-氨基水杨酸对大鼠实验性结肠炎中性粒细胞趋化、活化及凋亡的影响

目的 观察4-氨基水杨酸(4-ASA)对三硝基苯磺酸(TNBS)诱导的大鼠实验性结肠炎炎症损伤、肠组织一氧化氮合酶(iNOS)表达、血中性粒细胞(PMN)凋亡及血清白细胞介素(IL)-8水平等的影响,探讨4-ASA对炎症性肠病(IBD)的治疗作用及机制.方法 40只SD大鼠分为正常对照组(n=10)和实验组(n=30),实验组建立大鼠结肠炎模型.建模第5天将实验组按照处理方式分为实验对照组(n=10,0.9%氯化钠1 ml灌肠),5-ASA组[n=10,5-ASA液(200 mg/kg)1 ml灌肠]和4-ASA组[n=10,4-ASA液(200 mg/kg)1 ml灌肠].连续治疗7 d后处死动物,取病变段肠组织,行结肠大体损伤及结肠组织学损伤评分;生化法检测髓过氧化物酶活性;免疫组化法检测肠组织iNOS表达量;流式细胞术检测血PMN凋亡率;酶联免疫吸附法检测血清IL-8浓度.结果 经4-ASA治疗7d后,4-ASA组大鼠体重明显较实验对照组增加(P<0.01,t=14.09);疾病活动指数评分、大体评分、组织学评分和MPO活性显著较实验对照组降低(t值分别=7.87、18.37、6.66和19.60,P值均<0.01).而5-ASA组与4-ASA组间上述各指标差异均无统计学意义(P值均>0.05).实验对照组肠组织iNOS表达率为(73.55±5.15)%,较正常对照组显著增加[(5.95±1.45)%,t=39.93,P<0.01)];5-ASA和4-AsA组大鼠肠组织iNOS表达率分别为(37.80±3.82)%和(42.27±3.52)%,均较实验对照组显著降低(t值分别=17.62和15.76,P值均<0.01).实验对照组血清IL-8的平均浓度明显高于正常对照组(t=25.25,P<0.01);5-ASA和4-ASA组明显低于实验对照组(t值分别=12.31和11.57,P值均<0.01).实验对照组血PMN凋亡率明显低于正常对照组(t=11.48,P<0.01);5-ASA和4-ASA组凋亡率明显高于实验对照组(t值分别=7.51和10.47,P值均<0.01).结论 4-ASA灌肠对实验性结肠炎大鼠具有显著的治疗作用,其治疗机制可能与降低PMN的趋化与激活、上调血PMN凋亡率、减少肠组织局部损伤因子有关.     

Reactions of superoxide with myeloperoxidase and its products

Myeloperoxidase (MPO) uses hydrogen peroxide to oxidize chloride to hypochlorous acid. It also converts numerous substrates to reactive free radicals. When released by neutrophils, the enzyme operates in the presence of a flux of superoxide. We show that superoxide has a profound influence on oxidative reactions catalysed by MPO. It reacts directly with the enzyme to modulate production of hypochlorous acid. Within neutrophil phagosomes, where MPO functions to kill micro-organisms, it may be the preferred substrate for the enzyme. Superoxide also reacts rapidly with radicals generated by MPO, e.g. from tyrosine and tyrosyl peptides. Initial products are organic peroxides. These species are likely to be toxic and contribute to the pathophysiological actions of MPO.     

Oral 4-aminosalicylic acid versus 5-aminosalicylic acid slow release tablets. Double blind, controlled pilot study in the maintenance treatment of Crohn's ileocolitis.

4-Aminosalicylic acid (4-ASA) has been suggested as an effective treatment for both active and quiescent ulcerative colitis. 5-Aminosalicylic acid (5-ASA) is well accepted for the maintenance treatment of inactive ulcerative colitis. Moreover, recent studies suggest that 5-ASA may also be effective in maintaining remission in Crohn's colitis. As treatment with 4-ASA may result in less side effects, the efficacy of a one year's maintenance treatment with oral 4-ASA (1.5 g/d, slow release tablets, n = 19) and oral 5-ASA (1.5 g/d, slow release tablets, n = 21) was compared in a double blind, randomised trial in patients with quiescent Crohn's ileocolitis. Patients with ileocolonic or colonic involvement were enrolled if in stable remission for more than two months but less than one year. Baseline demography and clinical severity were similar in both groups. Total colonoscopy and ileoscopy were performed at enrollment and at the end of the study. After one year seven of 19 patients receiving 4-ASA (36%) and 8 of 21 receiving 5-ASA (38%) had developed a clinical relapse, as defined by a rise in the Crohn's disease activity index (CDAI) of more than 100 points to values higher than 150. The relapse rates between the 4-ASA and the 5-ASA groups were not statistically different although no comparison with the spontaneous relapse rate in a placebo group could be made. Clinical relapse was accompanied by a statistically significant rise in serum concentrations of soluble interleukin 2 receptor and by an increased percentage of activated peripheral blood T cells. There were no statistical differences between the 4-ASA and the 5-ASA groups regarding the height of rise in CDAI or of soluble interleukin 2 receptor concentrations during relapse, thus showing a similar severity relapsed disease activity. In conclusion, 4-ASA maybe as effective as 5-ASA in the maintenance treatment of quiescent Crohn's disease and there were no differences in the severity of relapse between both treatment groups.     

Mechanisms of resistance of Aspergillus fumigatus Conidia to killing by neutrophils in vitro

Despite the critical role for neutrophils in host defenses against invasive aspergillosis, previous studies have established that neutrophils are unable to kill resting conidia of Aspergillus fumigatus. The mechanisms of resistance of the conidia were therefore investigated. Electron microscopy studies showed the fusion of phagosomes containing A. fumigatus conidia with lysosomes of the neutrophil. Resting conidia of A. fumigatus were then compared with those that had been preincubated in broth until swollen, but not germinated, as well as with blastospores of Candida albicans (two fungal forms that are killed by neutrophils) and zymosan particles. Despite comparable susceptibility to phagocytosis, resting conidia of A. fumigatus stimulated production of significantly less superoxide anion, hydrogen peroxide, and hypochlorous acid and induced less myeloperoxidase-dependent iodination by neutrophils than did the preincubated conidia of A. fumigatus, blastospores of C. albicans, or zymosan particles. In addition, resting conidia of A. fumigatus were relatively resistant to cell-free killing by oxidants presumed to be generated by neutrophils. Thus, resistance of resting conidia of A. fumigatus to neutrophil fungicidal mechanisms appears to be secondary to both failure of the conidia to stimulate an optimal respiratory burst as well as resistance of the conidia to neutrophil oxidants. However, the reversal of this resistance by preincubation of the conidia suggests that neutrophils still may form an important host defense against the conidia of A. fumigatus.     

5-Aminosalicylic acid prevents oxidant mediated damage of glyceraldehyde-3-phosphate dehydrogenase in colon epithelial cells

Background—Reactiveoxygen and nitrogen derived species produced by activated neutrophilshave been implicated in the damage of mucosal proteins including theinhibition of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in theactive inflammatory lesion in patients with inflammatory bowel disease(IBD). This study investigated the efficacy of currently used IBDtherapeutics to prevent injury mediated by reactive oxygen and nitrogenderived species.
Methods—GAPDH activityof human colon epithelial cells was used as a sensitive indicator ofinjury produced by reactive oxygen and nitrogen derived species. HCT116cells (10⁶/ml phosphate buffered saline; 37°C) wereincubated in the presence of 5-aminosalicylic acid (5-ASA),6-mercaptopurine, methylprednisolone, or metronidazole before exposureto H₂O₂, HOCl, or NO in vitro. HCT116 cellGAPDH enzyme activity was determined by standard procedures. Cell freereactions between 5-ASA and HOCl were analysed by spectrophotometry andfluorimetry to characterise the mechanism of oxidant scavenging.
Results—GAPDH activityof HCT116 cells was inhibited by the oxidants tested: the concentrationthat produced 50% inhibition (IC₅₀) was 44.5 (2.1) µMfor HOCl, 379.8 (21.3) µM for H₂O₂, and 685.8 (103.8) µM for NO (means (SEM)). 5-ASA was the only therapeutic compound tested to show efficacy (p<0.05) against HOCl mediated inhibition of enzyme activity; however, it was ineffective against H₂O₂ and NO mediated inhibition of GAPDH.Methylprednisolone, metronidazole, and the thiol-containing6-mercaptopurine were ineffective against all oxidants. Studies atratios of HOCl:5-ASA achievable in the mucosa showed direct scavengingto be the mechanism of protection of GAPDH activity. Mixing 5-ASA andHOCl before addition to the cells resulted in significantly greaterprotection of GAPDH activity than when HOCl was added to cellspreincubated with 5-ASA. The addition of 5-ASA after HOCl exposure didnot restore GAPDH activity.
Conclusions—Therapiesbased on 5-ASA may play a direct role in scavenging the potentneutrophil oxidant HOCl, thereby protecting mucosal GAPDH fromoxidative inhibition. These findings suggest that strategies for thefurther development of new HOCl scavenging compounds may be useful inthe treatment of IBD.

Keywords:5-aminosalicylic acid; 6-mercaptopurine; prednisolone; metronidazole; oxidants; glyceraldehyde-3-phosphatedehydrogenase

     

Putting rectal 5-aminosalicylic acid in its place: the role in distal ulcerative colitis

Oral aminosalicylates such as sulfasalazine and mesalamine are widely prescribed for the treatment of mild or moderately active distal ulcerative colitis. However, a critical review of the literature demonstrates that rectal 5-aminosalicylic acid (5-ASA) is the optimal therapy for this disease. Meta-analyses of published trials show that rectally delivered 5-ASA is superior to placebo and to conventional rectal corticosteroids in inducing remission of distal ulcerative colitis, whereas the combination of rectal 5-ASA with a rectal corticosteroid or oral aminosalicylate is superior to rectal 5-ASA alone. For maintaining remission of distal ulcerative colitis, rectal 5-ASA is significantly better than placebo and at least as effective as oral 5-ASA. The dosage forms available for rectal delivery include suppositories, foams, and liquid enemas, and selection among these preparations should be guided by the proximal extent of disease and patient preference. The efficacy of rectal 5-ASA is complemented by its low rate of reported adverse effects, which may reflect its reduced potential for systemic absorption. This review summarizes the evidence supporting the role of rectal 5-ASA as a first-line therapy for mild or moderately active distal ulcerative colitis, and offers guidelines for its use.     

Optimum dosage of 5-aminosalicylic acid as rectal enemas in patients with active ulcerative colitis.

5-Aminosalicylic acid (5-ASA), the active moiety of sulphasalazine (SASP), was given as a rectal enema to patients with mild to moderate distal ulcerative colitis to determine the minimum effective dosage. A double blind study was carried out using enemas containing 1, 2, or 4 g or 5-ASA or placebo for a one month treatment period. One hundred and thirteen patients with ulcerative colitis attending our outpatient clinic volunteered to participate. Clinical, sigmoidoscopic, and histological assessments were carried out at the beginning of the study and after 15 and 30 days of treatment. All patients who received 5-ASA enemas showed significantly better results than those who received a placebo enema (p less than 0.001) but no difference was detected among the patients receiving differing concentrations of 5-ASA. This study suggests that 1 g 5-ASA (in a 100 ml enema) is a sufficient dosage for patients with a mild to moderate attack of ulcerative colitis.     

Chronic interstitial nephritis induced by 5-aminosalicylic acid: a new case report

5-aminosalicylic acid (5-ASA) used for the treatment of inflammatory bowel disease is known to induce chronic interstitial nephritis (CIN). However, the frequency of occurrence and the spectrum of severity of 5-ASA-induced CIN are not known. In this paper, we report a new case of CIN induced by 5-ASA in a patient treated for about 7 years for a Crohn disease. After that 5-ASA was discontinued and prednisone therapy started, renal function improved partially. About 30 observations of CIN induced by the use of 5-ASA in patients treated for inflammatory bowel disease have already been published. None were published in patients treated for other diseases such as arthritis rheumatism. The review of the literature suggests that the prognosis is poor and correlates with the duration of treatment, the cumulative dose and the level of renal impairment at diagnostic. We believe that the control of the renal function in patients treated by 5-ASA must be regular and prolonged.